Virtual Private LAN Service (VPLS) is a Layer 2 Virtual Private Network (L2VPN) technology based on Multi-Protocol Label Switching (MPLS) and Ethernet. VPLS enables multipoint-to-multipoint VPN networking. It provides a better solution for operators that use a point-to-point L2VPN and may simplify the management of internal routing information.
In a VPLS network, generally, fully connected pseudo wires (PWs) are required between Provider Edge (PE) devices, but this solution is not good for expansion of the network. Hierarchical VPLS (H-VPLS), unlike VPLS, requires only fully connected PWs between Network Provider Edge (NPE) devices and a User-facing Provider Edge (UPE) device only needs to connect to the NPE. The H-VPLS solution better suits the hierarchical network structure and enables easier deployment of VPLS networks.
The prior art provides an operator backbone Ethernet architecture called Provider Backbone Bridges (PBB), which uses MAC-in-MAC encapsulation to re-encapsulate Ethernet packets in a UPE with the Backbone Media Access Control (B-MAC) address of an Backbone Edge Bridge (BEB) to hide the Customer Media Access Control (C-MAC) address of the user. The NPE only needs to proceed according to the B-MAC address.
The UPE learns the mapping between the B-MAC address and the C-MAC address from data packets of the user. When the UPE receives a packet from the Customer Edge (CE), the UPE finds the corresponding Customer Destination MAC (C-DMAC) address in the MAC address table, finds the corresponding B-MAC address according to the C-DMAC address, and adds the B-MAC address to the Backbone Destination MAC (B-DMAC) address field of the MAC address table. The NPE only needs to learn the B-MAC address of the UPE so that the MAC addresses to be learned by the NPE are fewer and that the H-VPLS system is more scalable. Moreover, when the Customer Premises Network (CPN) changes, the position of the B-MAC address does not change and the NPE does not need to re-learn the MAC address and thus the impact, caused by unnecessary packets, on the network is relieved.
Label Distribution Protocol (LSP) based VPLS defines a MAC Address Withdraw message. In a multi-homing network, when the switchover of the active and standby links takes place, the MAC Address Withdraw message is used to notify the far end to remove the corresponding MAC address.
As shown in FIG. 1, the CE is dual-homed and connected to both UPE1 and UPE2, where the CE-UPE1 link is an active link and the CE-UPE2 link is a standby link. Then, in the corresponding VPLS, all NPEs learn only the B-MAC address of the UPE while the UPE needs to learn the mapping between the B-MAC address and the C-MAC address. When the CE-UPE1 link fails, the CE-UPE2 link works as the active link instead. In this case, UPE2 may send a MAC Address Withdraw message which carries an empty MAC address table, and the related NPE and UPE devices in the VPLS will remove all MAC addresses. The NPE and UPE devices need to learn MAC addresses again.
In addition, the MAC Address Withdraw method also defines a MAC address table that is able to remove a specified MAC address. However, in the network shown in FIG. 1, because CEs change randomly, it is hard for UPE2 to know all MAC addresses of the CEs. In this case, the only choice is to let the MAC Address Withdraw message carry an empty MAC address table. Devices receiving the MAC Address Withdraw message will remove all MAC addresses of the corresponding Virtual Switch Instance (VSI). The NPE and UPE devices must learn MAC addresses again. The VSI is configured to map physical access links of the VPLS to virtual links.
During implementation of the present invention, the inventor finds that large numbers of unicast packets exist in the process of MAC address learning by the NPE and UPE, and impact the network.